To remove the Avast Antivirus software in Windows 7, locate the program in the Programs and Features section of the Control Panel, and uninstall it. If that fails, download the Avast uninstall utility from the Support section on Avast.com, boot Windows in Safe Mode, and run the utility.
To close Avast Antivirus, right click on its icon in the taskbar, and select the Open User Interface option. Disable the self-defense module, access the task manager by right-clicking on the taskbar and clicking Task Manger, select Avast Antivirus, and click on the End Process button. To uninstall the program, click on Start, select the Control Panel option, and click on the Programs icon. Click on the Programs and Features link, select the Avast Antivirus software in the list, and click Uninstall.
To download the Avast uninstall utility, navigate to Avast.com, click on the Product and Support button, click on Support, click on Downloads, and select the Uninstall Utility option. After downloading the utility, start Windows in Safe Mode by restarting the computer, tapping F8 while the system is booting up and selecting the Safe Mode option. After that, start the Avast uninstall utility by double-clicking on the downloaded executable file, click on the Remove button, and restarting your computer. If you installed Avast Antivirus to a location other than the default one, click on Browse, and select the installation folder before clicking Remove.